Soluble Ligand of the Immune Checkpoint Receptor (sPD-L1) in Blood Serum of Patients with Renal Cell Carcinoma

PD-L1 as a Urine Biomarker in Renal Cell Carcinoma-A Case Series and Proof-of-Concept Study

BACKGROUND

Renal cell carcinoma (RCC) is among the most lethal urologic malignancies once metastatic. Current treatment approaches for metastatic RCC (mRCC) involve immune checkpoint inhibitors (ICIs) that target the PD-L1/PD-1 axis. High PD-L1 expression in tumor tissue has been identified as a negative prognostic factor in RCC. However, the role of PD-L1 as a liquid biomarker has not yet been fully explored. Herein, we analyze urine levels of PD-L1 in mRCC patients before and after either ICI therapy or surgical intervention, as well as in a series of patients with treatment-naïve RCC.

PATIENTS AND METHODS

The mid-stream urine of patients with mRCC (n = 4) or treatment-naïve RCC, i.e., prior to surgery from two centers (cohort I, n = 49: cohort II, n = 29) was analyzed for PD-L1 by ELISA. The results from cohort I were compared to a control group consisting of patients treated for non-malignant urologic diseases (n = 31). In the mRCC group, urine PD-L1 levels were measured before and after tumor nephrectomy (n = 1) or before and after ICI therapy (n = 3). Exosomal PD-L1 in the urine was analyzed in selected patients by immunoblotting.

RESULTS

A strong decrease in urine PD-L1 levels was found after tumor nephrectomy or following systemic treatment with ICIs. In patients with treatment-naïve RCC (cohort I), urine PD-L1 levels were significantly elevated in the RCC group in comparison to the control group (median 59 pg/mL vs. 25.7 pg/mL, p = 0.011). PD-L1 urine levels were found to be elevated, in particular, in low-grade RCCs in cohorts I and II. Exosomal PD-L1 was detected in the urine of a subset of patients.

CONCLUSION

In this proof-of-concept study, we show that PD-L1 can be detected in the urine of RCC patients. Urine PD-L1 levels were found to correlate with the treatment response in mRCC patients and were significantly elevated in treatment-naïve RCC patients.

Serum sPD-L1 levels are elevated in patients with viral diseases, bacterial sepsis or in patients with impaired renal function compared to healthy blood donors

OBJECTIVES

Immune checkpoints play an important role in maintaining the balance of the immune system and in the development of autoimmune diseases. A central checkpoint molecule is the programmed cell death protein 1 (PD-1, CD279) which is typically located on the surface of T cells. Its primary ligand PD-L1 is expressed on antigen presenting cells and on cancer cells. Several variants of PD-L1 exist, among these soluble molecules (sPD-L1) present in serum at low concentrations. sPD-L1 was found elevated in cancer and several other diseases. sPD-L1 in infectious diseases has received relatively little attention so far and is therefore subject of this study.

METHODS

sPD-L1 serum levels were determined in 170 patients with viral infections (influenza, varicella, measles, Dengue fever, SARS-CoV2) or bacterial sepsis by ELISA and compared to the levels obtained in 11 healthy controls.

RESULTS

Patients with viral infections and bacterial sepsis generally show significantly higher sPD-L1 serum levels compared to healthy donors, except for varicella samples where results do not reach significance. sPD-L1 is increased in patients with impaired renal function compared to those with normal renal function, and sPD-L1 correlates significantly with serum creatinine. Among sepsis patients with normal renal function, sPD-L1 serum levels are significantly higher in Gram-negative sepsis compared to Gram-positive sepsis. In addition, in sepsis patients with impaired renal function, sPD-L1 correlates positively with ferritin and negatively with transferrin.

CONCLUSIONS

sPD-L1 serum levels are significantly elevated in patients with sepsis, influenza, mesasles, Dengue fever or SARS-CoV2. Highest levels are detectable in patients with measles and Dengue fever. Also impaired renal function causes an increase in levels of sPD-L1. As a consequence, renal function has to be taken into account in the interpretation of sPD-L1 levels in patients.

Soluble programmed cell death-ligand 1 as a new potential biomarker associated with acute coronary syndrome

Background

Soluble programmed cell death-ligand 1 (sPD-L1) has been well documented to activate immunosuppression and is considered an essential predictor of negative clinical outcomes for several malignances and inflammatory conditions. However, the clinical significance of sPD-L1 in the peripheral blood of patients with coronary artery disease (CAD) remains unclear. The aim of this study was to assess the correlations of sPD-L1 with clinical features in CAD patients and evaluate the diagnostic value of this protein in CAD.

Methods

A total of 111 CAD patients and 97 healthy volunteers who served as healthy controls (HCs) were consecutively enrolled. Plasma levels of sPD-L1 were measured with an amplified enzyme-linked immunosorbent assay (ELISA), and hs-CRP was measured with a C-reactive protein assay kit. The levels of other inflammatory cytokines were assessed in 88 CAD patients and 47 HCs by a multiparameter immunoluminescence flow cytometry detection technique. A logistic regression model was used to assess the independent association of sPD-L1 with acute coronary syndrome (ACS). The correlation between sPD-L1 and inflammatory cytokines in ACS was also assessed.

Results

Plasma levels of sPD-L1 were significantly increased in CAD patients, especially those with ACS. Univariate logistic regression analysis revealed that sPD-L1 (OR: 3.382, 95% CI: 2.249–5.084, p < 0.001), BMI, hypertension, diabetes, dyslipidemia, previous MI, and the levels of HDL-C, LDL-C and hs-CRP were significantly associated with ACS. sPD-L1 (OR: 3.336, 95% CI: 1.084–6.167, p = 0.001) was found to be independently and significantly associated with ACS in the subsequent multivariable logistic regression analysis. Additionally, elevated plasma sPD-L1 levels were associated with increased interleukin-6 and interleukin-8 levels in ACS patients. Receiver operating characteristic (ROC) analysis showed that the AUC of sPD-L1 for diagnosing ACS was 0.778, with a sensitivity of 73.9% and a specificity of 73.4%, which was comparable with that of the inflammatory biomarker hs-CRP.

Conclusion

The plasma sPD-L1 level reflects the severity of CAD, is associated with inflammatory responses and is a potential new biomarker for the diagnosis of ACS.

Soluble forms of PD-1/PD-L immune checkpoint receptor and ligand in blood serum of breast cancer patients: association with clinical pathologic factors and molecular type of the tumor

Results of enzyme-linked immunosorbent assay of the soluble forms of PD-1/PD-L immune checkpoint receptor and ligand (sPD-1 and sPD-L1) in pretreatment blood serum of 88 breast cancer patients at various disease stages aged 30-83 years are presented. The control group included 55 practically healthy women aged 19-82 years. Serum sPD-1 and sPD-L1 levels in breast cancer patients highly significantly (p<0.0001) differ from control and these changes are opposite: soluble receptor level is more than 6-fold decreased, while soluble ligand concentration - 5.5 fold increased. Both markers separately, as well as their ratio demonstrate very high sensitivity (94-100%) and specificity (95-100%) in relation to healthy control. No statistically significant associations of sPD-1 and sPD-L1 levels with clinical stage, individual TNM system criteria, tumor histological structure, grade, receptor status, and molecular type were established. In particular, no significant peculiarities of the markers' levels in triple negative breast cancer successfully treated with anti-PD-1/PD-L1 preparations were revealed. Long-term follow-up and dynamic studies of sPD-1 and sPD-L1serum levels in the course of treatment are required for evaluation of their independent from clinical and morphological factors prognostic significance and the possibility of application as low invasive tests for prediction and monitoring of corresponding targeted therapy efficiency.

Soluble Levels of CD163, PD-L1, and IL-10 in Renal Cell Carcinoma Patients

CD163+ M2 macrophages have been suggested to counteract tumor immunity by increasing immunosuppressive mechanisms including PD-L1 and IL-10 expression. Soluble levels of PD-L1, IL-10, and CD163 have been reported as potential biomarkers in various cancers, although the prognostic value in renal cell carcinoma (RCC) has to be further elucidated. In the present study, we measured the levels of sPD-L1, sIL-10, and sCD163 in 144 blood samples from patients with RCC. The levels were determined by using enzyme linked immunosorbent assays. Soluble PD-L1 and CD163 were detectable in 100% of the serum samples, and sCD163 in 22% of the urine samples, while only a minority of the samples had detectable sIL-10. Significantly higher serum levels of sPD-L1 and sCD163 were observed in patients with metastatic disease (p < 0.05). The results also showed that patients with high levels of sPD-L1 in serum had shorter cancer-specific survival compared with patients with low levels (p = 0.002). The results indicate that sPD-L1 most significantly reflects tumor progression in RCC.

Non-cytomembrane PD-L1: An atypical target for cancer

Programmed death ligand 1 (PD-L1) has conventionally been considered as a type I transmembrane protein that can interact with its receptor, programmed cell death 1 (PD-1), thus inducing T cell deactivation and immune escape. However, targeting the PD-1/PD-L1 axis has achieved adequate clinical responses in very few specific malignancies. Recent studies have explored the extracellularly and subcellularly located PD-L1, namely, nuclear PD-L1 (nPD-L1), cytoplasmic PD-L1 (cPD-L1), soluble PD-L1 (sPD-L1), and extracellular vesicle PD-L1 (EV PD-L1), which might shed light on the resistance to anti-PD1/PDL1 therapy. In this review, we summarize the four atypical localizations of PD-L1 with a focus on their novel functions, such as gene transcription regulation, therapeutic efficacy prediction, and resistance to various cancer therapies. Additionally, we highlight that non-cytomembrane PD-L1s are of significant cancer diagnostic value and are promising therapeutic targets to treat cancer.

Prognostic Significance of Serum PD-L1 Level in Patients with Locally Advanced or Metastatic Esophageal Squamous Cell Carcinoma Treated with Combination Cytotoxic Chemotherapy

Background

There are no useful biomarkers for the clinical outcome of advanced esophageal squamous cell carcinoma (ESCC). In this study, we aimed to investigate the prognostic value of soluble PD-L1 (sPD-L1) in serum of patients with locally advanced or metastatic ESCC who received cytotoxic chemotherapy as first-line treatment.

Materials and Methods

This study evaluated the expression pattern of PD-L1 by immunohistochemistry and sPD-L1 concentration, and correlation with clinicopathological factors and overall survival (OS) in 190 patients with ESCC.

Results

sPD-L1 concentration was highly expressed in ESCC, especially in female patients. Patients with a high sPD-L1 level (≥0.63 ng/mL) had a shorter OS than those with a low sPD-L1 level (<0.63 ng/mL). In a multivariate analysis, high sPD-L1 concentration remained an independent prognostic factor of OS after adjustment for possible confounders. However, tissue PD-L1 expression level was non-prognostic in this study.

Conclusion

There was no significant correlation between serum sPD-L1 concentration and tissue PD-L1 expression level. sPD-L1 concentration before treatment could be an effective and convenient biomarker of prognosis in patients with locally advanced or metastatic ESCC treated with combination cytotoxic chemotherapy.

High Serum PD-L1 Levels Are Associated with Poor Survival in Urothelial Cancer Patients Treated with Chemotherapy and Immune Checkpoint Inhibitor Therapy

Serum PD-L1 (sPD-L1) levels are associated with prognosis in various tumors but has not yet been investigated in advanced bladder cancer. We assessed pretreatment serum samples from 83 BC patients who received platinum chemotherapy and from 12 patients who underwent immune checkpoint inhibitor (ICI) therapy. In addition, on-treatment samples from further therapy cycles were collected during chemotherapy (n = 58) and ICI therapy (n = 11). Serum PD-L1 levels were determined using ELISA. High baseline sPD-L1 levels were associated with worse ECOG status (p = 0.007) and shorter overall survival for both chemotherapy- and ICI-treated patients (p = 0.002 and p = 0.040, respectively). Multivariate analysis revealed high baseline sPD-L1 level as an independent predictor of poor survival for platinum-treated patients (p = 0.002). A correlation analysis between serum concentrations of PD-L1 and matrix metalloprotease-7 (MMP-7)-a protease which was recently found to cleave PD-L1-revealed a positive correlation (p = 0.001). No significant sPD-L1 changes were detected during chemotherapy, while in contrast we found a strong, 25-fold increase in sPD-L1 levels during atezolizumab treatment. In conclusion, our work demonstrates that pretreatment sPD-L1 levels are associated with a poor prognosis of BC patients undergoing platinum and ICI therapy. Future research should prospectively address the value of sPD-L1 in predicting treatment response.

Prognostic significance of soluble forms of immune checkpoint PD-1/PDL1 receptor and ligand in blood plasma of gastric cancer patients

Analysis of long-term treatment results of 101 primary gastric cancer patients at various stages of the tumor process followed during 1 - 41 months (median - 6,4 months) from the onset of specific treatment are presented depending on the levels of soluble forms (s) of PD-1 receptor and its ligand PD-L1 in blood plasma. Overall survival assessed by Kaplan-Meyer analysis and with the help of Cox multiparametric regression model was applied as the criterion of prognostic value. It was found that at high (≥ 35 pg/ml) sPD-L1 levels in blood plasma, the overall survival of patients with gastric cancer was statistically significantly lower than at the marker's levels below 35 pg / ml (p <0.045): 1-year survival comprised 78 and 96%, 2-year - 52 and 78%; 3-year - 40 and 61% at high and low sPD-L1 respectively. Median survival of patients with high plasma sPD-L1 comprised 29 months, of those with low sPD-L1 was not achieved during the whole follow-up period. This trend was observed not only in the total group of stage I-IV gastric cancer patients, but also in patients at the early stages of the disease, though sPD-L1 did not show an independent prognostic value in multiparametric model. At the same time, the overall survival of patients with gastric cancer did not depend on the baseline levels sPD-1 in blood plasma. Thus, soluble ligand sPD-L1 can be considered as a potentially valuable factor for prognosis of gastric cancer patients' survival, and, probably, of anti-PD-1/PD-L1 treatment efficiency, but further studies and patients' monitoring are required to prove this statement.

The clinical implication of soluble PD-L1 (sPD-L1) in patients with breast cancer and its biological function in regulating the function of T lymphocyte

This work investigated the clinical prognostic implications and biological function of plasma soluble programmed cell death ligand 1 in breast cancer patients. Plasma sPD-L1 levels of recurrent/metastatic breast cancer patients were determined, and the association of sPD-L1 levels and metastatic progression-free survival and metastatic overall survival was assessed. The PD-L1 expression on breast cancer cells was analyzed by flow cytometry, and the level of sPD-L1 in the supernatant of breast cancer cells was determined by enzyme-linked immunosorbent assay. Furthermore, the effect of sPD-L1 on the proliferation and apoptosis of T lymphocytes was detected by WST-1 assay and flow cytometry. The plasma sPD-L1 levels in 208 patients with recurrent/metastatic breast cancer before receiving first-line rescue therapy were measured. The optimal cutoff value of plasma sPD-L1 for predicting disease progression was 8.774 ng/ml. Univariate and multivariate analyses identified high sPD-L1 level (≥ 8.774 ng/ml) and visceral metastasis were independent factors associated with poor prognosis. Relevance analysis showed that the plasma sPD-L1 level was weakly

associated with some systemic inflammation markers, including white cell count (WBC), absolute monocyte

count, and absolute neutrophil count. Furthermore, we found sPD-L1 could be found in supernatant of culture with breast cancer cell line expressing PD-L1 on the cell surface and inhibit T lymphocyte function, playing a negative regulatory role in cellular immunity. sPD-L1 was a good tumor predictive maker in breast cancer and it may play a potentially important role in immune tolerance.

Soluble forms of PD-L1 and PD-1 as prognostic and predictive markers of sunitinib efficacy in patients with metastatic clear cell renal cell carcinoma

Metastatic clear cell renal cell carcinoma (mccRCC) benefits from several treatment options in the first-line setting with VEGFR inhibitors and/or immunotherapy including anti-PD-L1 or anti-PD1 agents. Identification of predictive biomarkers is highly needed to optimize patient care. Circulating markers could reflect the biology of metastatic disease. Therefore, we evaluated soluble forms of PD-L1 (sPD-L1) and PD-1 (sPD-1) in mccRCC patients. The levels of sPD-L1 and sPD-1 were evaluated from plasma samples of mccRCC patients before they received a first-line treatment (T0) by the VEGFR inhibitor sunitinib (50 patients) or by the anti-VEGF bevacizumab (37 patients). The levels of sPD-L1 and sPD-1 were correlated to clinical parameters and progression-free survival (PFS). High levels of sPD-1 or sPDL1 were not correlated to PFS under bevacizumab while they were independent prognostic factors of PFS in the sunitinib group. Patients with high T0 plasmatic levels of sPD-L1 had a shorter PFS (11.3 vs 22.5 months, p = .011) in the sunitinib group. Equivalent shorter PFS was found with high levels of sPD-1 (8.6 vs 14.1 months, p = .009). mccRCC patients with high plasmatic levels of sPD-L1 or sPD-1 are poor responders to sunitinib. sPD-L1 or sPD-1 could be a valuable tool to guide the optimal treatment strategy including VEGFR inhibitor.

Key Immune Checkpoint PD-1/PD-L1 Signaling Pathway Components in the Blood Serum from Patients with Bone Tumors

The levels of sPD-1 and sPD-L1 were analyzed in blood serum of 132 patients (age 14-70 years) with primary bone tumors: osteosarcoma (N=39), chondrosarcoma (N=42), Ewing sarcoma (N=9), chordoma (N=12), giant-cell bone tumor (GCBT) (N=16), benign neoplasms (N=14) and in and practically healthy subjects (age 19-58 years; N=27). sPD-L1 levels in all studied bone neoplasms were significantly higher than in the control. Serum sPD-1 level in GCBT patients was significantly higher than in the control, benign neoplasms, chondrosarcoma, and chordoma patients, but did not differ from osteosarcoma group. sPD-1 concentration in Ewing sarcoma was significantly higher than in chordoma and chondrosarcoma, but did not differ from the control. sPD-1 level in chondrosarcoma patients was also lower than in osteosarcoma, Ewing sarcoma, and in the control. Both sPD-1 and sPD-L1 concentrations were not significantly associated with the type of affected bone, process localization, disease stage, tumor histological grade, patients' age and sex. These results suggest the possibility of using these biological markers for preliminary assessment of the character of the process in the bone.

Baseline plasma levels of soluble PD-1, PD-L1, and BTN3A1 predict response to nivolumab treatment in patients with metastatic renal cell carcinoma: a step toward a biomarker for therapeutic decisions

Despite a proportion of renal cancer patients can experiment marked and durable responses to immune-checkpoint inhibitors, the treatment efficacy is widely variable and identifying the patient who will benefit from immunotherapy remains an issue. We performed a prospective study to investigate if soluble forms of the immune-checkpoints PD-1 (sPD-1), PD-L1 (sPD-L1), pan-BTN3As, BTN3A1, and BTN2A1, could be candidate to predict the response to immune-checkpoint blockade therapy. We evaluated the plasma levels in a learning cohort of metastatic clear cell renal carcinoma (mccRCC) patients treated with the anti-PD-1 agent nivolumab by ad hoc developed ELISA’s. Using specific cut-offs determined through ROC curves, we showed that high baseline levels of sPD-1 (>2.11 ng/ml), sPD-L1 (>0.66 ng/ml), and sBTN3A1 (>6.84 ng/ml) were associated with a longer progression-free survival (PFS) to nivolumab treatment [median PFS, levels above thresholds: sPD-1, 20.7 months (p < .0001); sPD-L1, 19 months (p < .0001); sBTN3A1, 17.5 months (p = .002)]. High sPD-1 and sBTN3A1 levels were also associated with best overall response by RECIST and objective response of >20%. The results were confirmed in a validation cohort of 20 mccRCC patients. The analysis of plasma dynamic changes after nivolumab showed a statistically significant decrease of sPD-1 after 2 cycles (Day 28) in the long-responder patients. Our study revealed that the plasma levels of sPD-1, sPD-L1, and sBTN3A1 can predict response to nivolumab, discriminating responders from non-responders already at therapy baseline, with the advantages of non-invasive sample collection and real-time monitoring that allow to evaluate the dynamic changes during cancer evolution and treatment.

Association between serum level soluble programmed cell death ligand 1 and prognosis in patients with non-small cell lung cancer treated with anti-PD-1 antibody

Background

Programmed cell death ligand 1 (PD‐L1) is known to have soluble forms aside from its membrane‐bound forms. The aim of this study was to evaluate the predictive and prognostic values of serum soluble PD‐L1 (sPD‐L1) in patients with non‐small cell lung cancer (NSCLC) who were treated with anti‐PD‐1 antibody.

Methods

A total of 233 patients were enrolled in this study. We assessed the level of serum sPD‐L1 before anti‐PD‐1 antibody treatment (pembrolizumab or nivolumab) and evaluated the correlation with PD‐L1 expression on tumor cells, the response to anti‐PD‐1 antibody treatment, and patient outcome.

Results

The median serum sPD‐L1 concentration was 67.7 (range, 25 to 223) pg/mL. A weak correlation between serum sPD‐L1 and tumor PD‐L1 expression was observed. The disease control rate in the high sPD‐L1 group (≥90 pg/mL) was significantly lower than that in the low sPD‐L1 group (<90 pg/mL) (37% vs. 57%, P = 0.0158). The progression‐free survival (PFS) and overall survival (OS) in the high sPD‐L1 group were significantly shorter than those in the low sPD‐L1 group (median PFS, 57 days vs. 177 days, P = 0.011; median OS, 182 days vs. not reached, P < 0.001). The high level of serum sPD‐L1 was independently associated with a shorter PFS (hazard ratio [HR], 1.910; P = 0.061) and OS (HR, 2.073; P = 0.034) in multivariate analysis.

Conclusions

The serum sPD‐L1 level, which was only weakly correlated with the tumor PD‐L1 expression level, was an independent predictive and prognostic biomarker for NSCLC patients receiving anti‐PD‐1 antibody.

Key points

Significant findings of the study

The disease control rate in the high sPD‐L1 group was significantly lower than that in the low sPD‐L1 group. The progression‐free survival (PFS) and overall survival (OS) in the high sPD‐L1 group were significantly shorter than those in the low sPD‐L1 group. The high level of serum sPD‐L1 was independently associated with a shorter PFS and OS in multivariate analysis.

What this study adds

This study demonstrated that serum sPD‐L1 level was an independent predictive and prognostic biomarker for NSCLC patients receiving anti‐PD‐1 antibody.

Prognostic impacts of tumoral expression and serum levels of PD-L1 and CTLA-4 in colorectal cancer patients

BACKGROUND

Programmed cell death ligand-1 (PD-L1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) play a pivotal role in cancer immunotherapy. Each of these molecules has a membrane-bound receptor form (mPD-L1/mCTLA-4) and a soluble form (sPD-L1/sCTLA-4). However, these prognostic impacts in colorectal cancer (CRC) remain unclear.

METHODS

We immunohistochemically scored tumoral mPD-L1/mCTLA-4 expression and quantified preoperative circulating sPD-L1/sCTLA-4 levels using matched serum specimens from 131 patients with pStage I-III CRC. We also examined the association between these statuses and tumor infiltrating lymphocytes (TILs) in these patients.

RESULTS

Elevated levels of mPD-L1, mCTLA-4, sPD-L1 and sCTLA-4 were significantly correlated with poor overall survival (OS) and disease-free survival (DFS). Co-high expression of tumoral mPD-L1 and mCTLA-4 or co-elevated levels of serum sPD-L1 and sCTLA-4 were strongly correlated with poor OS and DFS. Multivariate analysis revealed that both statuses were negative independent prognostic factors for OS [hazard ratio (HR) 3.86, 95% confidence interval (95% CI) 1.71-8.51, p = 0.001; HR 5.72, 95% CI 1.87-14.54, p = 0.004, respectively] and DFS (HR 2.53, 95% CI 1.23-4.95, p = 0.01; HR 6.88, 95% CI 2.42-17.13, p = 0.0008, respectively). Although low expression of tumoral mCTLA-4 was significantly correlated with increased CD8(+) TILs, there was no correlation in any other combination.

CONCLUSIONS

We verified the prognostic impacts of mPD-L1, mCTLA-4, sPD-L1 and sCTLA-4 in pStage I-III CRC patients. Dual evaluation of immune checkpoint molecules in primary tissues or preoperative serum could identify a patient population with poor prognosis in these patients.

The Clinical Significance of Soluble Programmed Cell Death-Ligand 1 (sPD-L1) in Patients With Gliomas

Background: Soluble PD-L1 (sPD-L1) in the circulation has been documented to activate global immunosuppression and is considered a predictor of negative clinical outcomes in several malignances. However, the clinical significance of sPD-L1 in the peripheral blood and cerebrospinal fluid (CSF) of patients with glioma remains unclear.

Objective: The aim of this study was to detect the correlations of sPD-L1 with clinical features in brain tumors and assess the diagnostic value of this protein in gliomas.

Methods: Serum samples were obtained from 73 patients with glioma, 20 patients with meningioma, and 49 healthy controls (HCs) in this study. In total, 31 CSF samples were collected from the matched glioma patients, and seven samples were collected from the matched meningioma patients. The expression of serum sPD-L1 in the glioma cohort was followed for 20 days after surgery to examine the kinetics in the circulation. Inflammatory markers were evaluated based on preoperative blood parameters. The sPD-L1 levels in the serum and CSF were determined by enzyme-linked immunosorbent assay (ELISA). The logistic regression model was used to assess the independent associations of sPD-L1 with gliomas, including high-grade gliomas.

Results: Serum and CSF levels of sPD-L1 were significantly elevated in patients with gliomas compared to those with meningiomas and HCs. Additionally, increased levels of sPD-L1 were observed in relatively advanced tumors. sPD-L1 overexpression in the CSF appears to be more representative of aggressive tumor features than overexpression in the serum. For glioma diagnosis, both serum and CSF sPD-L1 showed significant value in the diagnosis and stratification of glioma, and the best diagnostic performance was obtained with serum sPD-L1 rather than blood-based inflammatory markers. In addition, a descending trend in the level of serum sPD-L1 was observed in postoperative patients.

Conclusion: In gliomas, elevated circulating and CSF sPD-L1 levels are associated with aggressive biological activities. The results of the current study suggest that sPD-L1 is a promising biomarker for gliomas that can be used in clinical practice.

Soluble forms of immune checkpoint receptor PD-1 and its ligand PD-L1 in plasma of patients with ovarian neoplasms

Background:Ovarian cancer is one of the most common oncologic diseases holding the frst place in mortality related to neoplasms of female genitalia. Along with active surgical intervention, contemporary ovarian cancer treatment includes various chemotherapeutic regimens which in many cases are quite effective, but relapse and death rates still remain high. In the recent years, major attention has been paid to the possibility of ovarian cancer immunotherapy associated with the discovery of the so-called “immune checkpoint” signaling, i.e. programmed cell death-1 / programmed death-ligand 1 (PD-1/PD-L) pathway, controlling intensity and duration of autoimmune response at physiologic conditions. Tumor PD-1 and/or PD-L1 expression is being actively studied as a predictor of anti-PD-1/PD-L treatment efficacy; however, this approach has certain limitations and problems that might be probably bypassed by determination of soluble PD-1 (sPD-1) and its ligand (sPD-L1) in serum or plasma.

Aim:Comparative evaluation of sPD-1 and sPD-L1 content in plasma of healthy women and of patients with benign or borderline ovarian tumors and ovarian cancer, as well as the analysis of associations between these markers and main clinical and pathologic characteristics of ovarian cancer.

Materials and methods:Sixty two (62) patients with ovarian neoplasms aged 32 to 77 (median, 56.5) years were enrolled into the study. Fifteen (15) patients had benign tumors, 9 had borderline, and 38, ovarian cancer. The control group included 17 healthy women aged 24 to 67 (median, 49) years. Plasma sPD-L1 and sPD-1 concentrations were measured with standard enzyme immunoassay kits (Afmetrix, eBioscience, USA).

Results:Plasma sPD-L1 and sPD-1 levels in ovarian cancer patients (median, 41.3 and 48.0 pg/ml, respectively) did not differ significantly from those in the control group (49.5 and 43.8 pg/ml). sPD-L1 level in the patients with benign tumors (median, 22.2 pg/ml) was signifcantly lower than in the control (p < 0.01). The lowest sPD-1 level in plasma was found in the patients with borderline ovarian neoplasms, the difference with the ovarian cancer group being statistically signifcant (p < 0.05). No correlations between sPD-L1 and sPD-1 plasma levels were found in any of the study groups. sPD-L1 level signifcantly increased with disease stage (R = 0.44; p < 0.01), the most signifcant increase being observed at the most advanced IIIC stage (p < 0.05 as compared to all other stages). sPD-L1 was also signifcantly higher in the patients with ascites than in those without ascites. Plasma sPD-1 concentration was not associated with the indices of ovarian cancer progression, though its median was 1.3–1.44 times lower in the stage I than in the stage II–III patients, and decreased in those with the tumor size above 10 cm (assessed by ultrasound examination) and in the patients with ascites. No statistically signifcant associations of the markers' levels with tumor histological type and differentiation grade of ovarian cancer were found.

Conclusion:sPD-L1 level in ovarian cancer patients correlates with disease progression and can be considered as a promising marker for monitoring of anti-PD-1/PD-L1 treatment efficacy. Potential clinical implications of sPD-1 require further studies.